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which habitually breed in the galls formed by true gall-makers, and which, as they 
feed on the substance of the gall itself and only occasionally or incidentally destroy 
the gall-making insect, may be appropriately considered as ‘‘ Inquilines” or Guest- 
flies. Mr. Walsh enumerates five species of willow, Salix discolor, Muhl., which 
yields three distinct galls; S. cordata, Muhl., which yields six galls; S. longifolia, 
Muhl., which yields three; 8. nigra, Marshall, which yields two galls, aud 8. humilis, 
Marshall, which yields no less than ten distinct galls; some of these galls, however, 
occur on more than one species of willow. Besides the true galls, a Coleopterous 
pseudo-gall was found on Salix longifolia. Of twenty-one undoubtedly distinct galls, 
twelve are made by Diptera (Cecidomyidz) and six by Hymenoptera (Tenthredinide). 
In addition to a great number of insects which occasionally inhabit these galls, there 
are, of true inquilines, which seem to inhabit them exclusively, but without confining 
themselves to one particular species of gall, seven Cecidomyidous species, two Tenthre- 
dinidous species, and at least one, and probably four or five Coleoptera, besides seven 
species of Micro-Lepidoptera. The author points out the danger of mistaking inqui- 
lines for the true makers of the gall, and gives numerous instances in which saw-flies 
are inquilinous in the galls ef gall-gnats, and gall-gnats inquilinous in the galls of 
saw-flies. The same gall is often inhabited by several different species of inquilines, 
and many species of guests habitually live in the galls of several different species of 
hosts. Occasionally one and the same species is sometimes inquilinous in the galls of 
other insects, and sometimes attacks natural substances in no wise connected with 
galls. ‘‘ Nothing gives us a better idea of the prodigious exuberance of insect life 
and of the manner in. which one insect is often dependent upon another for its very 
existence, than to count up the species which haunt, either habitually or occasionally, 
one of these willow galls, and live either upon the substance of the gall itself or upon 
the bodies of other insects that live upon the substance of the gall. In the single 
gall, Salicis brassicoides, n. sp., there dwells the Cecidomyia which is the maker of the 
gall—four inquilinous Cecidomyie—an inquilinous saw-fly—five distinct species of 
Micro-Lepidoptera, some feeding on the external leaves of the gall, and some burrow- 
ing into the heart of the cabbage, but scarcely ever penetrating into the central cell so 
as to destroy the larva that provides them with food and lodging—two or three 
Coleoptera—a Psocus (Pseudo-Neuroptera)—a Heteropterous insect found abundantly 
in several other willow-galls—an Aphis, which is also found on the leaves of the willow, 
but particularly affects this gall—and, preying on the Aphides, the larva of a Chrysopa 
(Neuroptera) and the larva of a Syrphide (Diptera)—besides four or five species of 
Chalcidide, one Braconide Ichneumon, and one Tachinide, which prey upon the 
Cecidomyize and the Micro-Lepidoptera ; making altogether about two dozen distinct 
species, and representing every one of the eight Orders, if with Sieboldt, Erichson, and 
Hagen, we refer Pseudo-Neuroptera to Orthoptera.” 
Referring to the alleged discovery of Wagner that the larve of Cecidomyia breed 
young ones,—that a second generation of larve is developed within the bodies of the 
first, —the author expresses his firm belief that the young larve which crept out of the 
bodies of Cecidomyta larve were nothing but larve of Chalcidide or Proctotrupide, 
several species of which he knew from experience to breed inside the bodies of larva | 
of willow Cecidomyiew. As to Wagner’s statement that the same newly-born larve 
went through the same process a second time, he believes it to be a pure and simple | 
delusion. 
Mr. F. Smith was in possession of numerous rose-galls, from which had | 
